GPS system with IMUs tracks first responders

PORTLAND, Ore.—Tracking devices vendor TRX Systems Inc. last week unveiled a plan to enable people or things to be tracked with pinpoint accuracy regardless of whether they are outside, inside or in the presence of electronic jamming.

Global Positioning System devices can help track first responders, unmanned areal vehicles, soldiers and expensive assets, but require an inertial measurement unit (IMU) to work when GPS-signals are unavailable, such as in tunnels, inside buildings, or when electronic interference is present. The TRX solution, which includes Analog Devices Inc.’s ultra-small MEMS-based IMU, aims to solve that problem.

"We are working with firefighter and other gear makers to integrate our tracking unit into their uniforms, which can tell not only the person's location, within a couple of meters, but can also tell which direction they are going, whether they are going up or down stairs, whether they are standing or crawling and so forth," said Carol Politi, CEO of TRX Systems (Greenbelt, Md.).

The IMU chosen by TRX for its design will be ADI's newest 10-degree-of-freedom IMU that houses a three-axis MEMS gyroscope, a three-axis MEMS accelerometer, and three-axis magnetometer and a barometric pressure sensor in a cube measuring just 23 millimeter on a side.

"We believe the ADIS16407 is the only 10 degree-of-freedom IMU that is small enough, accurate enough and inexpensive enough for integration with first responders uniforms, unmanned vehicles, and the like," said Bob Scannell, iSensor business development manager with ADI’s MEMS/Sensors Technology Group. "Our IMU enables TRX's Sentrix Tracking Unit to keep track of assets inside office buildings, warehouses, tunnels, caves, mines, ‘urban canyons’ and other GPS-denied environments."

ADI claims its IMUs can track motion through up to 300 degrees per second, can survive shocks of up to 2,000-Gs, and is fully calibrated at the factory for turnkey installation and integration by original equipment manufacturers (OEMs). When installed in TRX's Sentrix, managers can view the location, heading, orientation and other vital information about personnel using a laptop computer.

What is the incremental cost of this new IMU technology on top of a supporting GPS? It would be interesting to see where else it could be used. As a 23 mm cube = 1 square inch, it sounds like it is still too large (or was there an error in the dimensions in the article) to incorporate into a mobile phone. How much might the pricing come down with high volume production? If affordable (and small enough), it would be a natural replacement for any GPS system to improve accuracy when out of range of the satellites.

IMUs have been available for years, as part of the inertial guidance systems of everything from ships to spacecraft to missiles. However, by incorporating cheap MEMS sensors, instead of expensive ring-laser gyros, TRX and other OEMs are bringing down the price of location tracking for a variety of applications, from finding people to protecting important assets.